ovl: plumb through flush method

Filesystems can implement their own flush method that release
resources, or manipulate caches. Currently if one of these
filesystems is used with overlayfs, the flush method is not called.

[Amir: fix fd leak in ovl_flush()]

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index dbfb35fb0ff7921aa4cad53104b583b1cc69dbc9..6e454a2940469e715bf5f53c7e4ddf102cb13cd5 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -686,6 +686,26 @@ static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
                            remap_flags, op);
 }
 
+static int ovl_flush(struct file *file, fl_owner_t id)
+{
+       struct fd real;
+       const struct cred *old_cred;
+       int err;
+
+       err = ovl_real_fdget(file, &real);
+       if (err)
+               return err;
+
+       if (real.file->f_op->flush) {
+               old_cred = ovl_override_creds(file_inode(file)->i_sb);
+               err = real.file->f_op->flush(real.file, id);
+               revert_creds(old_cred);
+       }
+       fdput(real);
+
+       return err;
+}
+
 const struct file_operations ovl_file_operations = {
        .open           = ovl_open,
        .release        = ovl_release,
@@ -697,6 +717,7 @@ const struct file_operations ovl_file_operations = {
        .fallocate      = ovl_fallocate,
        .fadvise        = ovl_fadvise,
        .unlocked_ioctl = ovl_ioctl,
+       .flush          = ovl_flush,
 #ifdef CONFIG_COMPAT
        .compat_ioctl   = ovl_compat_ioctl,
 #endif